JPS6112540B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a resistance change rate detection circuit for a humidity sensing element, and more particularly to a resistance change rate detection circuit suitable for obtaining a humidity control device that compensates for the delay in operation of a humidity sensing element. .

Conventionally, moisture sensing elements have been used to prevent fogging on car windows, to prevent condensation on video tape recorder heads, and to adjust humidity in air conditioners. It is generally known to operate a humidity control device.

As shown in FIG. 1, this kind of moisture-sensitive element is preferably one having a characteristic that the impedance, for example, the resistance value R, changes substantially linearly with respect to changes in relative humidity. It is known that it can be used as a humidity sensing element.

However, this type of humidity sensing element has the disadvantage that the resistance value change follows humidity changes slowly, that is, the humidity response is slow, and the humidity response is particularly poor when the humidity changes from low humidity to high humidity. Although efforts are being made to develop a moisture-sensitive element that does not have this drawback, it appears that nothing satisfactory has yet been achieved. Therefore, when humidity control is performed using this type of humidity sensing element, the humidity control device operates at a much higher humidity than the preset humidity due to poor humidity response, or there is a considerable time delay. The problem was that the desired humidity control could not be achieved as it was.

The present invention has been made in view of the above circumstances, and it is an object of the present invention to provide a resistance value change rate detection circuit suitable for obtaining a humidity control device that compensates for the delay in operation of a humidity sensing element.

In order to achieve the above object, the present invention includes a resistance-voltage conversion circuit that converts a change in the resistance value of a humidity sensing element whose resistance value changes in response to a change in humidity into a change in voltage; A level detection circuit that generates a first pulse from a first output terminal when the input reaches a first set voltage due to a change in humidity, and generates a second pulse from a second output terminal when the input reaches a second set voltage. and a logic gate circuit that is connected to the level detection circuit and generates an output when a second pulse is input within a predetermined time after the input of the first pulse, and the output of the logic gate circuit causes the humidity sensing to be detected. The present invention provides a resistance value change rate detection circuit for a moisture sensitive element, which is characterized in that it determines whether the resistance value change rate of the element exceeds a predetermined level.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Before describing one embodiment of the present invention in detail with reference to the drawings, the response characteristics of this type of moisture-sensitive element to humidity will first be explained in order to better understand the content of the present invention. For example, FIG. 2 shows an example of the response characteristic curve A of this type of humidity sensitive element when the relative humidity changes from 40% to 90%. In Figure 2, the resistance value at time t = 0 is R ₀ , and the resistance value at relative humidity of 40% in Figure 1 is R _0.
shall be equal to relative humidity rapidly from 40%
Suppose it changes to 90%. The resistance value t ₁ second after this change is R ₁ . A further minute time Δ from this time t ₁
The resistance value at time t ₂ (t ₂ = t ₁ +Δt) after t has passed is R ₂
(R ₂ =R ₁ -ΔR), and the resistance value at time t ₃ becomes R ₃ in the same manner. This value of R ₃ corresponds to the steady resistance value at 90% relative humidity in FIG.

When controlling humidity to prevent condensation using a humidity sensing element having a characteristic curve as shown in FIG. 2, it is assumed that, for example, a hot wire heater is operated at a relative humidity of 90% to prevent condensation. In this case, it takes only t ₃ seconds for the resistance value of the humidity sensing element to reach the steady resistance value R ₃ at a preset relative humidity of 90%, resulting in a delay in operation. Still there
For example, ΔR/Δt at time t ₁ before ₃ seconds have elapsed.
(Δt is a minute time after time t ₁ , ΔR is the range of change in resistance value that changes within this minute time), and ΔR/Δt means the slope of response characteristic curve A at time t ₁ . Therefore, when this value is large, it means that the resistance value is changing rapidly, which means that the humidity in the atmosphere around the humidity sensing element is higher than the humidity indicated by the resistance value. Become.
Therefore, for example, if ΔR/Δt is determined at time t ₁ and this value is equal to or greater than a predetermined value, the hot wire heater is activated early at this point, thereby reliably compensating for the delay in activation of the moisture-sensitive element. .

The present invention has been made based on the above-mentioned viewpoints, and one embodiment of the present invention will now be described with reference to FIG.
In Fig. 3, reference numeral 1 denotes a humidity sensing element such as a ceramic sensor whose resistance changes in response to changes in humidity, and is installed inside a device or indoors for humidity control. )It is connected to the. 2
1 is a resistance voltage conversion circuit connected to the humidity sensing element 1, and is a circuit that converts a change in resistance due to a change in humidity of the humidity sensing element 1 into a change in voltage. 3 is a level detection circuit which inputs the output of the conversion circuit 2, and when this input reaches a first set voltage, generates a first pulse from its first output terminal 4, and when the input reaches a second set voltage, a second pulse is generated. A second pulse is generated from the output terminal 5. A logic gate circuit that generates an output when a second pulse is input within a predetermined time after inputting the first pulse is connected to the first and second output terminals 4 and 5 of the level detection circuit 3 to detect the rate of change in resistance value. Configure the circuit. In the embodiment shown in Figure 3, this logic gate circuit comprises a monostable multivibrator 6 and an AND gate circuit 7, and the first output terminal 4 of the level detection circuit 3 is connected to the input terminal of the monostable multivibrator. and its second output terminal 5 is AND
It is connected to the first input terminal of the gate circuit 7, and the output terminal of the monostable multivibrator 6 is connected to its second input terminal.

Next, the operation of the embodiment shown in FIG. 3 will be explained.
While the humidity in the atmosphere is low, the resistance value R of the humidity sensing element 1
is larger than R ₁ in FIG. 2, the voltage is input from the resistance-voltage conversion circuit 2 to the level detection circuit 3, and since the voltage does not reach either the first set voltage or the second set voltage, the voltage is input to the first and second output terminals. The outputs from 4 and 5 become logic "0", and therefore the output of AND gate circuit 7 also becomes logic "0". Next, suppose that the humidity suddenly rises. At this time, the resistance value of the humidity sensing element 1 becomes _R1 first, so the level detection circuit 3 detects the input voltage _V1 corresponding to the resistance value _R1 , and sets this input voltage _V1 as the first set voltage. When this happens, a first pulse is generated from the first output terminal 4. Therefore, the monostable multivibrator 6 is triggered by this first pulse, becomes active, and outputs a logic "1" for a certain period of time, which is then output to the AND gate circuit 7.
is applied to the second input terminal of. The time during which the monostable multivibrator 6 outputs logic "1" corresponds to the time Δt in FIG. 2. When the resistance value R of the humidity sensing element 1 becomes equal to or less than _R2 within the time period Δt, the level detection circuit 3 detects the input voltage _V2 corresponding to _R2 , and sets this as the second set voltage. A second pulse is generated from the second output terminal 5 and an output of logic "1" is applied to the first input terminal of the AND gate circuit 7. Therefore, the AND gate circuit 7 has 2
The individual theory “1” is added at the same time.
A logic “1” is output from the AND gate circuit 7. As is clear from the above, AND gate circuit 7
The output becomes logic "1" when the resistance value R of the humidity sensing element 1 becomes less than R ₁ and within a minute time of Δt.
is further limited to when _R2 or less. That is, only when the humidity in the atmosphere changes rapidly and the resistance change rate ΔR/Δt of the humidity sensing element 1 exceeds the set value R ₁ −R ₂ /Δt, the AND gate circuit 7 outputs a logic “1”. Therefore, it is possible to determine whether the rate of change in resistance value of the humidity sensing element 1 exceeds a predetermined level. Therefore, if the output of logic "1" from the AND gate circuit 7 is detected and the humidity control device etc. is controlled at an early stage, humidity control due to poor humidity response of the humidity sensing element can be avoided. It is possible to reliably compensate for the delay in the operation of the

FIG. 4 is a block diagram of a control system in an embodiment of a humidity control device in which a resistance value change rate detection circuit according to the present invention is applied to a humidity control circuit to compensate for a delay in the operation of a humidity sensing element.

In FIG. 4, the same parts as those shown in FIG. 3 will be described with the same reference numerals. The circuit shown in FIG. 4 connects a timer 8 to the output terminal of the AND gate circuit 7 shown in FIG.
A Schmitt circuit 9 is connected to the first input terminal of the gate circuit 10 and to the output terminal of the resistance-voltage conversion circuit 2, and its output terminal is connected to the OR gate circuit 10.
A drive circuit 11 for humidity control is connected to the output terminal of the controller.

Next, the operation of the device shown in FIG. 4 will be explained. For example, the operation will be explained when the humidity suddenly changes from low humidity to high humidity. In this case, as explained with reference to FIG. 3 above, the humidity responsiveness of the humidity sensing element 1 is poor, so it is unable to follow the changes in humidity in the atmosphere, and the resistance value has not yet exceeded the predetermined set value. The output of the Schmitt circuit 9 becomes logic "0" and logic "0" is input to the second input terminal of the OR gate circuit 10, so that the drive circuit 11 for humidity control does not operate. However, since the resistance change rate exceeds a predetermined set value due to a sudden change in humidity, the level detection circuit 3 outputs a logic "1" signal as explained with reference to FIG.
The timer 8 is activated by the output from the gate circuit 7, and during the predetermined operating time of the timer 8, the output of logic "1" from the timer 8 is inputted to the first input terminal of the OR gate circuit 10, and the drive circuit 11 for humidity control is inputted. is operated for a predetermined period of time to control the load 12 such as a heater.
The humidity is controlled in this way, but after a predetermined period of time has elapsed, the timer 8 stops operating and its output becomes "0". However, at this stage, the delayed operation of the moisture sensing element 1 is activated and its resistance value becomes less than the set value, so the output from the Schmitt circuit 9 becomes logic "1" and the second input terminal of the OR gate circuit 10. When a logic "1" is input to , the humidity control drive circuit 11 operates according to the resistance level of the humidity sensing element 1 to control the load 12 and adjust the humidity, thereby compensating for the delay in operation. This makes it possible to control humidity.

FIG. 5 shows an example of a specific circuit of each block in the block diagram of FIG. 4, and the same parts are given the same reference numerals. Description of each part within each of these blocks will be omitted.

The above describes one embodiment of the present invention, and the resistance-voltage conversion circuit according to the present invention,
Of course, circuits other than those shown in the above embodiments can also be applied to the level detection circuit, logic gate circuit, etc.

[Brief explanation of the drawing]

Figure 1 is a characteristic diagram showing the relationship between relative humidity and resistance of the ceramic humidity sensing element, Figure 2 is a characteristic curve diagram showing the humidity response characteristics of the ceramic humidity sensing element shown in Figure 1, and Figure 3 is a characteristic curve diagram showing the relationship between relative humidity and resistance of the ceramic humidity sensing element. A block diagram of an embodiment of the present invention, FIG. 4 is a block diagram of an embodiment in which the one in FIG. 3 is applied to a humidity control device, and FIG. 5 is a specific circuit diagram of each block in FIG. 4. An example is shown below. In the figure, 1...moisture sensing element, 2...resistance-voltage conversion circuit, 3...level detection circuit, 4, 5...output terminal, 6...monostable multivibrator, 7...
AND gate circuit, 8...timer, 9...Schmitt circuit, 10...OR gate circuit, 11...drive circuit, 12...load.

Claims (1)

[Claims] 1. A resistor that converts a change in resistance value of a humidity sensing element whose resistance value changes in response to a change in humidity into a change in voltage.
A voltage conversion circuit, the output of this conversion circuit is input, and when this input reaches a first set voltage due to a change in humidity, a first pulse is generated from a first output terminal, and when the input reaches a second set voltage, a first pulse is generated. A level detection circuit that generates a second pulse from two output terminals; and a logic gate circuit that is connected to the level detection circuit and generates an output when a second pulse is input within a predetermined time after input of the first pulse. A resistance value change rate detection circuit for a humidity sensing element, wherein it is determined based on the output of the logic gate circuit whether the resistance value change rate of the humidity sensing element exceeds a predetermined level. 2. The logic gate circuit according to claim 1 is composed of a monostable multivibrator and an AND gate circuit, and the first output terminal of the level detection circuit is connected to the input terminal of the monostable multivibrator. The second output terminal is connected to the first input terminal of the AND gate circuit, and the output terminal of the monostable multivibrator is connected to the second input terminal, and the resistance value of the moisture sensing element is determined by the output of the AND gate circuit. 2. The resistance change rate detection circuit for a moisture sensitive element according to claim 1, wherein the circuit determines whether the change rate exceeds a predetermined level.